1. Field of the Invention
The present invention relates to a rim holding apparatus and a rim width changing apparatus between upper and lower rims, which are applied to a tire uniformity machine.
2. Description of the Related Art
A tire uniformity machine is designed so that a tire is mounted on upper and lower spindles via upper and lower rims, and the uniformity etc. of the tire is measured by pressing a load wheel against the tire while rotating the tire around the axes of spindles. The parts of this tire uniformity machine have so far been configured as described below.
(1) FIG. 10 shows the relationship between a spindle external fitting portion and a rim inside. The spindle external fitting portions (upper and lower locking means 115 and 116) are arranged in parallel with the insides of rims 113 and 114 (for example, see Japanese Patent Provisional Publication No. 5-66171 (No. 66171/1993)). PA0 (2) FIG. 11 shows a rim drop preventive mechanism. The configuration is such that the drop of a rim 113 is prevented by using a n external hook-type drop preventive mechanism 144 to 146 attached to an external fixing side 109 of a spindle 101 (for example, see Japanese Patent Provisional Publication No. 5-66171 (No. 66171/1993)). PA0 (3) FIG. 12 shows a rim width changing apparatus between upper and lower rims. The configuration is such that the rim width is changed by using an external loader unit 247 to 265 and rims 213 and 214 (for example, see Japanese Patent Provisional Publication No. 3-257340 (No. 257340/1991)). PA0 (4) FIG. 13 shows another rim width changing apparatus between upper and lower rims. The configuration is such that only an upper rim 316 is moved vertically while being rotated with respect to an upper spindle 301, and an offset between a centerline CL (centerline in the width direction) between upper and lower rims 316 and 333 and a centerline CW (centerline in the width direction) of a load wheel LW is corrected by vertically moving a bearing housing 303 (upper and lower spindles 301 and 308) in the same direction (for example, see Japanese Patent Provisional Publication No. 3-188348 (No. 188348/1991)).
With the tire uniformity machine shown in FIGS. 10 to 12, a rim clamping device for parallel rims, which is of a hydraulic type, locks/unlocks parallel rims 113 and 114 and parallel spindles 101 and 102 by moving expanding/contracting rings 119 and 120 in relation to a piston. For this reason, during unlocking, the gap between the rim and spindle is very small (about 0.1 mm), being about 0.5 mm even in the case of expansion/contraction of a collet, for example, described in Japanese Patent Provisional Publication No. 7-190898 (No. 190898/1995). In this state, the rim is fitted onto and removed from the spindle. Therefore, when the rim is fitted or removed, positioning with accurate concentricity between the rim and spindle is needed, and also a liftable rim conveying device is needed.
On the tire uniformity machine shown in FIG. 11, hydraulic expanding/contracting rings 119 and 120 are used for a parallel rim holding mechanism. The expanding/contracting ring has a thickness as less as about 1 mm, so that wear and fatigue occur easily, resulting in low durability of the ring. Also, since the contact surface of the expanding/contracting ring in expansion constitutes a part of the structure, there is a risk of poor concentricity. Moreover, since the hydraulic expanding/contracting ring is held by a liquid pressure, there is a risk of poor concentricity of rim when a load is applied in the radial direction.
Also, on the above-mentioned tire uniformity machine, since the rim clamping device for parallel rims, which is of a hydraulic type, locks/unlocks the parallel rim 113 and parallel spindle 101 by moving the expanding/contracting ring in relation to the piston, there is a possibility for the parallel rim to drop when the hydraulic pressure is relieved. Therefore, the external rim drop preventive mechanism 144 to 146 is indispensable.
Also, on the above-mentioned tire uniformity machine, the fabrication of a rim fitting/removing portion wedge and the flow passage inside the ring and spindle is complicated.
Also, on the above-mentioned tire uniformity machine, the long spindle is divided into two pieces in consideration of the complicated fabrication and maintainability. When the spindle is assembled, therefore, highly accurate alignment of spindle is needed in order to ensure high rim runout accuracy.
On the tire uniformity machine shown in FIG. 12, when the upper and lower rim widths are changed, complicated loader movement such that the upper rim 213 is first set by an external loader and then the lower rim 214 is set is indispensable, so that much time i required for the rim width change due to the external loader unit 247 to 265.
Also, on the tire uniformity machine shown in FIG. 13, since only the upper rim is moved by an adapter 317 and spindle screw 307, the centerlines of the load wheel and tire shift from each other, which has some influence on the measurement results. Therefore, a moving mechanism must be added to the spindle itself to eliminate this shift (offset).
Also, on the above-mentioned tire uniformity machine, since only the upper rim is moved by an adapter 317 and spindle screw 307, the adapter 317 and the spindle 301 move in the axial direction while being rotated relatively. On the other hand, an O-ring etc. must be interposed between the adapter and spindle to seal the internal pressure of rim. However, when the adapter moves in the axial direction, because of the relative rotation of the adapter and spindle, the seal is rubbed each time the rim width is changed, so that early breakage or air leakage occurs.